1. Field of the Invention
The present invention relates to data backup systems and more particularly relates to systems and methods for emergency data backup.
2. Description of the Related Art
The explosion of data created by modem business systems such as e-business is motivating companies of all sizes to make storage a strategic investment priority. As storage takes precedence, two major concerns have emerged: business continuity and business efficiency. Business continuity requires storage that supports data availability so employees, customers and trading partners can access data continuously through reliable, disaster-tolerant systems. Business efficiency, where storage is concerned, requires investment protection, reduced total cost of ownership, and high performance and manageability.
In order to maintain the large amounts of data created and collected in these systems, storage area networks (SANs) have been developed. The Storage Network Industry Association (SNIA) defines a SAN as a network whose primary purpose is the transfer of data between computer systems and storage elements. A SAN may comprise a communication infrastructure, which provides physical connections; and a management layer, which organizes the connections, storage elements, and computer systems so that data transfer is secure and robust. A SAN may also be a storage system comprising storage elements, storage devices, computer systems, and/or appliances, plus all control software, communicating over a network.
Commonly, a storage area network includes a plurality of storage devices, such as tape drives or hard disk drives, connected over a network with a storage controller. The storage controller is generally a server that is configured to process read and write requests from a host and a plurality of connected client machines. The client machines often operate with a variety of operating systems. In large computing environments, the storage area network is an ideal solution for providing large amounts of storage and scalable server or storage controller performance.
Typically, in a storage area network environment, a client machine requests data from the storage controller. The storage controller then retrieves the data from the particular storage device that contains the requested data, often referred to as a home location. The storage controller then sends the data to the client machine. If the client machine modifies the data, the storage controller returns the modified data to the home location. Typically, the client machine awaits a response from the storage controller indicating that the read or write operation has completed. This controller-client interaction consumes storage controller resources and performance.
In order to improve storage controller performance and decrease resource usage, large amounts of RAM may be used to temporarily stage data. By staging data, the storage controller may indicate to the client machine that the read or write operation has been completed, and thereby recover system resources. By relying on RAM to temporarily stage the data, large corporations and institutions have been able to greatly increase data throughput and response time. However, in the event of a disaster, such as a power loss, the contents of the RAM are lost.
With the purpose of overcoming the power limitation of RAM memory, storage controllers are often coupled to an uninterruptible power supply (UPS). Generally, there are two types of UPS systems. The first is a standby power system (SPSs). An SPS monitors the power line and switches to battery power as soon as the SPS detects a problem. The switch to battery, however, can require several milliseconds, during which time the computer is not receiving any power. The second type of UPS is an on-line UPS. The on-line UPS avoids momentary power lapses by constantly providing power, even when the AC source is functioning properly. In general, on-line UPSs are much more expensive than SPSs.
One alternative solution to expensive UPSs is to dump or destage the data stored in memory to a local storage device, such as a hard disk drive. By dumping the data to a local disk, the modified data in the RAM is saved and a shut-down process may be completed earlier, thereby requiring a smaller, less expensive UPS system. One solution has been to write the modified data to a boot disk or a disk that contains an operating system. This solution requires no additional hardware, but with the increasing amounts of RAM in current storage controllers, this may be a slow process. Additionally, the shut-down process requires the use of the boot disk, and therefore the modified data dump competes with the shut-down process and therefore requires extra time. Time directly translates to product cost because a larger UPS system is required in order to supply power to the system while the shut-down process runs.
Another solution has been to implement a separate device to connect a data dump disk directly to the RAM or other memory module. While this system is effective and eliminates the conflicts with the boot disk, the device adds to the maintenance and cost of the storage controller.